The present invention relates to an ink jet print head comprising a container for conductive ink, provided with a capillary nozzle, a pair of electrodes disposed in the nozzle and facing each other across the nozzle, the ink forming a meniscus in the nozzle at a position such as to create a predetermined depth of ink between the electrodes and the meniscus, and wherein at least part of this depth of ink is expelled by selectively energizing the electrodes with voltage pulses such as to cause vaporization of a portion of ink by the effect of the current through the ink in the section of the nozzle between the electrodes.
Heads have been proposed for printing by means of a jet of ink from a nozzle, produced by the instantaneous vaporization of a portion of ink in the nozzle in such a way as to expel the layer of ink thereon. In one known head the ink is conductive and submerges a pair of electrodes which are disposed in facing relationship in a common plane perpendicular to the nozzle, whereby vaporization is caused by passing current through the ink, between the two electrodes. Such a head suffers from the disadvantage of generally requiring a relatively large nozzle diameter and, to avoid ink leakage, has the nozzle directed upwardly so that it is not possible to produce immediately readable printing.